Deborah McNaughton and Melinda Weinstein want us to face a simple truth — many people consume too many calories and their unhealthy eating is costing them a piece of prosperity.

"Life would be a whole lot easier if our bank accounts grew and our waistlines stayed in the lower-digit range," McNaughton and Weinstein write in their new book, "Rich and Thin: Slim Down, Shrink Debt & Turn Calories Into Cash."

This mother-and-daughter team has come up with an interesting twist on the typical personal finance book. The two provide a guide to building wealth by battling the bulge.

I like this approach to saving money and it's why I'm recommending "Rich and Thin" (McGraw Hill, $16.95) as the September selection for the Color of Money Book Club. McNaughton and Weinstein founded the Financial Victory Institute, which specialises in credit and financial education.

Their book could easily be dismissed because of its "let's all be healthy, wealthy and wise" shtick. But it's a fact that an increasing percentage of Americans are overweight. Sixty-six percent of US adults were overweight or obese in 2003 and 2004, according to researchers at the Johns Hopkins Bloomberg School of Public Health's Center for Human Nutrition.

Women aged 20 to 34 had the fastest rate of increase in obesity and being overweight. Eighty percent of black women aged 40 or over are overweight and 50 percent are obese. Minorities and low-income folks are disproportionately affected.

The researchers said if the rates continue at their current pace, 75 percent of adults and nearly 24 percent of US children and adolescents will be overweight or obese by 2015.

We know many adults are battling preventable illnesses because of their eating habits and lack of exercise. For example, an increasing number of Americans are developing Type 2 diabetes. About 40 percent of adults ages 40 to 74 — or 54 million people — have pre-diabetes, a condition that raises a person's risk of developing Type 2 diabetes, heart disease or stroke, according to the federal Centers for Disease Control.

African Americans are twice as likely as whites of similar age to develop diabetes, the CDC says. Hispanic Americans, American Indians, Asian Americans, and Pacific Islander Americans are also at particularly high risk of Type 2 diabetes.

The fact is that all that weight is crushing people's bank accounts. There's a cost to being unhealthy. You often pay more for insurance. But keep within a healthy weight range and you save. For example, starting in 2009 Indiana-based Clarian Health Partners plans to give employees a discount off their health insurance premiums for, among other things, not being overweight.

McNaughton and Weinstein's book contains a "Money Calorie Counter," which details how much you can save by investing the money not spent on foods that are unhealthy. For example, let's say you give up the expensive mocha latte you get five days a week. At about $3.35 a cup (with whip cream), you would save $871 and 104,000 calories per year. If you get a 69-cent donut, add another $179.40 a year and 46,800 calories. All told, that's $1,050.40 a year. If you were to put the money just from the latte in an investment each month that yields a 10 percent return over five years, you would have $5,620.64; in 10 years your money pot would grow to $14,868.33, and in 20 years you could have $55,117.52

"Think about the debt that could be paid off," the women say in their book.

The book contains several pages that show the cost, the pounds you pack on, and the money consumers spend on a variety of fast-food items, sandwiches, sweets and drinks. "Our Money Calorie Counter is not meant to deprive you of ever eating a chocolate bar, or having the latte you are craving," McNaughton and Weinstein write. "It is meant to make you aware of what you are spending your money on, and how you can cut back to save and build wealth."

Along with calorie-counting tips, you get the usual personal finance advice. The women cover budgeting, getting rid of debt and home buying. This is a slim book, but with a lot of good financial advice.

To become a member of the Color of Money Book Club, all you have to do is read the recommended book. I also invite you to join me online to chat with the authors. If you are interested in discussing this month's book selection, join me online at www.washingtonpost.com on Thursday, Sept. 27, at noon Eastern time. McNaughton and Weinstein will be available to take your questions on how to turn passed-up calories into cash.

In addition, every month I randomly select readers to receive a copy of the book, donated by the publisher. For a chance to win a copy of "Rich and Thin," send an e-mail to colorofmoney@washpost.com. Please include name and an address.

Listen to hear Michelle Singletary reports online go to www.npr.org. Readers can write c/o The Washington Post, 1150 15th St., N.W., Washington, D.C. 20071, or e-mail: singletarym@washpost.com. Comments and questions are welcome, but due to the volume of mail, personal responses may not be possible. Please also note comments or questions may be used in a future column, with the writer's name, unless a specific request to do otherwise is indicated.

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